I just noticed the other night that the tip of my WF line is sinking down into the water column. i would blame it on the weight I use for nymphing, but my strike indicator remains above water, while the tip of my fly line dips below the water. It is Cabelas Prestige Premier WF 5 wt. I bought it brand new last fall and have put probably 30 (maybe) trips on it since then. Is my fly line shot? I really hope not

A shot in the dark. Does it sink right away or after you've been fishing for a while? If you attached the leader with a nail knot and didn't seal the end of the flyline it could be wicking water as you fish???

it's a loop to loop connection, so the only way it would be getting water in it would be if it had a crack in it. I will have to pay attention to it next time I head out. I fished in a lot of weird currents, so maybe that's just causing the tip of the line to go under.

The tips of floating fly lines sink because there is less of the material between the core and coating that floats the line. The core and the coating of a fly line are a constant thickness; so as the line tapers, the material between the core and coating gets thinner and thinner.

In more expensive fly lines, they change the density of the material to compensate. Just like density compensated sinking lines use heavier material at the tips to get a even sink rate even as the line tapers, so expensive floating lines density compensate to keep the tips floating by lowering the density of the material as the line tapers. Cheaper lines do not do that, so their average density goes up as the line tapers down.

A fly line tip that is just a bit under water does not affect the drift of the fly. The water at the surface and the water just a few mms below the surface are moving in the same direction and at just about the same rate. So a tip just a bit under water does not cause increased drag.

What the sunken tip does do is to cause a bit more surface disturbance when you pick the line up to recast. So in spring creeks or "technical" water, you want the best fly line so you don't spook fish. For most fly fishing, it's not a big deal. Clean the line and put some line treatment on it. It will not be the reason you will or will not catch fish.

How does a line dressing work? If you are not interested, stop reading now.

You might wonder why putting a "floatant" or line "dressing" would help a fly line float. After all, the coating of a fly line is water proof so it cannot work by water proofing something that is already water proof.

Ever notice how water beads up on a car after it has been waxed? The wax does not waterproof the paint that is already waterproof. When water beads up, that water droplet is actually being repelled by forces at the molecular lever. The molecules in the line dressing are designed to repel the chemical "polar" or electrical forces that surround a water molecule.

This repulsive force can be measured by measuring can be measured by the "contact angle" of the water droplet.

The contact angle is the angle that a water droplet forms with the surface. The higher the contact angle, the greater the water repellency or hydrophobic property.

Here is a water droplet on a cloth treated with water repellant.

In the images above, the higher the water droplet is lifted above the solid surface, the greater the water repellency. Now think of this process in reverse with a solid fly line on the water surface. This repulsion of the fly line dressing by the water prevents the line from penetrating the water surface. It is the principle of the contact angle in reverse.

Now you know how line dressing works to float the line.

What is in the future? I think this is the next big step.

So far floating line technology has worked by making the fly line float by using specific gravity; ie, the lower the line mass density, the higher it will float. I predict that the next step will be to design the line surface to also actively repels water. Current modern line coatings self renew by leaching a slick coating to decrease line friction while casting. If that coating can be both slick and super hydrophobic, it would be a boon to floating fly lines. It keep the lines floating without having to treat them.

What everyone posted. Just ck your line for nicks & make sure it is sealed while dry so water isn't trapped in the tip. Keep it clean with dressing, grease up your leader & tippet. (Incidentally fluorocarbon leaders sink). & don't worry too much about it.

You say it's a loop to loop connection. Is it a welded loop made of the flyline material itself, or is it a braided monofilament loop slipped over the end of the flyline?

If it's a braided mono loop, the core of the line at the tip inside the braided loop may be exposed, which would allow it to wick up moisture and sink. One way to try to fix that would be to let the core dry out, then work a drop of Pliobond into the braided loop at the line tip to seal it. Then use Mucilin or a similar floatant on the mono braid material.

If it's a welded loop, use a magnifier to inspect the end of the line and see if there are any tiny cracks forming in the line coating near the loop or weld. If there are, water is probably wicking into the core through the cracks. After letting it dry out, you could try temporarily sealing the cracks with ArmorAll or a similar product, or you could cut off the tip below the cracks and replace it with a braided loop (and seal the cut end with Pliobond, as above).